Since this is a tad bit before my time, rarely shown and hard-to-find, I was unaware of it's existence until I saw a VHS copy of this listed on eBay. Of course I had to quickly investigate and bring it to my readers!
The Grinch stalks Whoville on Halloween night, along with his trusty sidekick Max, with intentions of spoiling the town festivities. But little Ukariah Who doesn't intend to let his plans come to fruition. This Halloween follow-up to "Dr. Seuss' How the Grinch Stole Christmas!" plays out more like a prequel since the Grinch still revels in his evil doing. It premiered on ABC Network on the evening of October 29, 1977. It won the 1977 Emmy Award for Outstanding Animated Program.
Part One . Part Two . Part Three
"Halloween is Grinch Night", also known as simply "Grinch Night" is available on this Dr. Seuss DVD collection: